1. Field of Invention
The invention relates to a restorative dental formulation and a method of its use for the temporary replacement of tooth structure and missing dental restorations.
2. Description of the Related Art
Tooth restoration is often accomplished by filling excavated cavities with a paste material, which is subsequently compacted and shaped to conform to the original contour of the tooth. Amalgams have been routinely employed as restoratives principally because of their durability. However, the metallic color is aesthetically unappealing. Also, biological interactions of the metallic components of dental amalgams are a concern. Tooth-colored restorative composites are usually composed of glass filler particles dispersed in methacrylate-type monomer resins. Additives such as pigments, initiators and stabilizers are also sometimes added to these compositions.
Resin-based dental restoratives have been disclosed that exhibit very favorable characteristics. For example, dental resins comprising friction-reducing additives, such as polytetrafluoroethylene have been disclosed in order to reduce wear due to friction (Temin U.S. Pat. No. 4,197,234). Fellman, et al. (U.S. Pat. No. 4,433,958) disclosed the addition of fluoropolymers as solid particulate in dental restorative compositions. Angeletakis (U.S. Pat. No. 6,395,803) discloses a resin-based dental restorative that has high condensability, low volumetric shrinkage, low shrinkage stress, higher loading, lower coefficient of thermal expansion and high wear and abrasion resistance.
Dental restoratives, such as crowns and bridges, are often used to address specific dental problems, including restoring a damaged tooth to its original shape, strengthening a tooth, or for cosmetic reasons. However, permanent restoratives are often not prepared in the dentist's office but require the involvement of a dental laboratory typically remote from the dentist's office. Additionally, dental problems arise remote from complete dental facilities such as when traveling to developing nations or in military operations. In these cases temporary dental restoratives must be utilized either until a permanent restorative can be fashioned or until a visit to more complete dental facilities can be made.
Temporary crowns and bridges are typically prepared in the dental office. The materials used for temporary restoratives are generally powder/liquid form or paste/paste form. In both forms, base material and a catalyst material are provided that causes the material to harden when the two are combined.
A temporary dental restorative material is generally dispensed using a powder/liquid system, with the base and catalyst components admixed in a specific ratio. The measured and admixed contents are then directly applied to the teeth.
In paste/paste systems, materials are most often provided in bulk cartridges having multiple chambers containing the separate components. The pastes are automatically mixed through a static mixer in predetermined volume ratios and then dispensed directly onto the teeth or dispensed onto a paper pad and then placed onto the teeth using a dental instrument.
A number of temporary restorative formulations currently exist. The most common restorative (provisional) formulations are zinc oxide based and contain eugenol (ZOE) or are glass-ionomer containing cements. Typically, glass-ionomer containing formulations offer greater durability over other, non-glass-ionomer compositions (Zanata, et al 2003). Additionally, many glass-ionomer formulations offer continuous release of fluoride (Hicks, et al, 2003). ZOE formulations, however, generally do not provide fluoride. Also, residual eugenol from temporary restorations can inhibit the setting of resins used to permanently restore the teeth (Paul, et al, 1997; Fujisawa, et al, 1997; Fonseca, et al, 2005).
Although glass-ionomer formulations exist, most have polyacids, the primary active ingredient, in the liquid portion of the formulation. The result is that within a relatively short period of time the polyacids, contained in the formulations, begin to form a gel. The net result is a shortened shelf life of the products, which is typically less than 2 years.
Packaging single-use devices for the mixing and delivery of dental restorative formulations has been disclosed. Ibsen, et al (U.S. Pat. No. 4,674,980) discloses a composite system wherein resin and exciplex members are stored separate from peroxide curing agents. The components are mixed just prior to use. Shellard, et al (U.S. application publication 2004/0033466) discloses a device for mixing and dispensing single doses of mixed paste/paste restorative formulations. In the disclosure by Shellard, catalyst and base components are in separate chambers. Mixing of the contents of the two chambers compartments occurs by applying pressure to an actuator which forces the contents of the chambers into a single tube and out through a tip. However, despite current packaging and dispensing methods, a visual, easy-to-use means for determining when restorative ingredients are properly mixed and ready for use is needed.